With the development of unmanned technology, development of unmanned ships has been progressing actively in order to perform operations which are dangerous and inefficient when being performed by a manned vessel among marine operations such as maritime investigation, marine reconnaissance and surveillance, marine accident response, and the like.
When operating an unmanned ship in the ocean, a method is employed in which the unmanned ship is mounted on a mother ship so as to execute a task when an operation is required and the unmanned ship is recovered to the mother ship after performing the task. This method has the advantage of reducing the time required to move the unmanned ship from land to sea and reducing the distance between the unmanned ship and a remote control station by installing the remote control station on the mother ship that monitors and controls the situation of the unmanned ship remotely. On the other hand, in order to operate the unmanned ship in this manner, a method of recovering the unmanned ship to the mother ship should be considered.
Various methods for recovering the unmanned ship to the mother ship have been developed. One of the various methods is to launch a heaving line provided in the unmanned ship to the mother ship and recover the unmanned ship when a crew hangs the heaving line on a crane or an electric winch.
In this case, a wire connected to the crane should be connected to the unmanned ship in order to recover the unmanned ship through the crane provided in the mother ship or the like. Since a crew is not carried on the unmanned ship, the crew should move from the mother ship to the unmanned ship to connect the wire, or should connect to the unmanned ship through a hook, or the like. However, there is a problem in that it is not easy to work in a sea with high waves. That is, there is a problem that a safety accident may occur when the crew gets on the unmanned ship and connects the wire. Therefore, a method for solving such a problem is required.